The sea surface covered by seaweed is now as big as South America

algae: A group of single-celled and multicellular organisms, once considered plants (they aren’t). As aquatic organisms, they grow in water. Like green plants, they depend on sunlight to make their food.

aquaculture: The process of raising fish and other aquatic species for human consumption. These activities are sometimes referred to as “fish farming.” People who work in this field are known as aquaculturists.

Atlantic: One of the world’s five oceans, it is second in size only to the Pacific. It separates Europe and Africa to the east from North and South America to the west.

attention: The phenomenon of focusing mental resources on a specific object or event.

bacteria: (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals). Bacteria are one of the three domains of life on Earth.

bladder: A flexible bag-like structure for holding liquids or gases.

bloom: (in microbiology) The rapid and largely uncontrolled growth of a species, such as algae in waterways enriched with nutrients.

Caribbean: The name of a sea that runs from the Atlantic Ocean in the East to Mexico and Central American nations in the West, and from the southern coasts of Cuba, the Dominican Republic and Puerto Rico down to the northern coasts of Venezuela and Brazil. The term is also used to refer to the culture of nations that border on or are islands in the sea.

coauthor: One of a group (two or more people) who together had prepared a written work, such as a book, report or research paper. Not all coauthors may have contributed equally.

coral: Marine animals that often produce a hard and stony exoskeleton and tend to live on reefs (the exoskeletons of dead ancestor corals).

current: A fluid — such as of water or air — that moves in a recognizable direction.

eel: A fish with a snake-like body and no scales. Many migrate from freshwater to salt water when it’s time to spawn. Note: Electric eels are not true eels but a type of knifefish.

fertilizer: Nitrogen, phosphorus and other plant nutrients added to soil, water or foliage to boost crop growth or to replenish nutrients that were lost earlier as they were used by plant roots or leaves.

global warming: The gradual increase in the overall temperature of Earth’s atmosphere due to the greenhouse effect. This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity.

habitat: The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.

machine learning: A technique in computer science that allows computers to learn from examples or experience. Machine learning is the basis of some forms of artificial intelligence (AI). For instance, a machine-learning system might compare X-rays of lung tissue in people with cancer and then compare these to whether and how long a patient survived after being given a particular treatment. In the future, that AI system might be able to look at a new patient’s lung scans and predict how well they will respond to a treatment.

macroalgae: These are multicellular species of algae, such as kelp and sargassum. They are large enough that individuals can be seen with the unaided eye. Indeed, some individuals can be meters (yards) long.

marine: Having to do with the ocean world or environment.

nitrogen: A colorless, odorless and nonreactive gaseous element that forms about 78 percent of Earth’s atmosphere. Its scientific symbol is N. Nitrogen is released in the form of nitrogen oxides as fossil fuels burn. Nitrogen is an important nutrient for living things.

nutrient: A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.

oceanographer: Someone who works in the branch of science that deals with the physical and biological properties and phenomena of the oceans.

oxygen: A gas that makes up about 21 percent of Earth’s atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).

Pacific: The largest of the world’s five oceans. It separates Asia and Australia to the west from North and South America to the east. The term can also refer to island nations that sit within the Pacific Ocean.

particle: A minute amount of something.

phosphorus: A highly reactive, nonmetallic element occurring naturally in phosphates. Its scientific symbol is P. It is an important part of many chemicals and structures that are found in cells, such as membranes, and DNA.

photosynthesis: (verb: photosynthesize) The process by which green plants and some other organisms use sunlight to produce foods from carbon dioxide and water.

range: The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists.

runoff: The rainwater that runs off of land into rivers, lakes and the seas. As that water travels through soils, it picks up bits of dirt and chemicals that it will later deposit as pollutants in streams, lakes and seas.

Sargassum: A genus of large brown marine algae, a type of seaweed. It floats and can develop into huge surface mats.

satellite: A moon orbiting a planet or a vehicle or other manufactured object that orbits some celestial body in space.

sea: An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

seaweed: Large algae growing in the sea or on rocks below the high-water mark.